Create objects from objects properties

Question

got the following array:

const myObjects = [{
    id: '1',
    name: 'name1',
    subs: [
        {
            id: '1',
            title: 'subName1'
        },
        {
            id: '2',
            title: 'subName2'
        }
    ]
},
{
    id: '2',
    name: 'name2',
    subs: [
        {
            id: '2',
            title: 'subName2'
        },
        {
            id: '3',
            title: 'subName3'
        }
    ]
}]

need to group by 'subs' values to create new array of objects with names of original objects they were into:

const mySubs = [
    {
        title: 'subName1',
        objects: ['name1']
    },
    {
        title: 'subName2',
        objects: ['name1', 'name1']
    },
    {
        title: 'subName3',
        objects: ['name2']
    }
]

Whats the best way to do this? Could lodash be of any help

Nina Scholz · Accepted Answer · 2020-02-26 13:29:08Z

1

You could group the data by title and collect name.

const
    objects = [{ id: '1', name: 'name1', subs: [{ id: '1', title: 'subName1' }, { id: '2', title: 'subName2' }] }, { id: '2', name: 'name2', subs: [{ id: '2', title: 'subName2' }, { id: '3', title: 'subName3' }] }],
    subs = Object.values(objects.reduce((r, { name, subs }) => {
        subs.forEach(({ title }) => {
            r[title] = r[title] || { title, objects: [] };
            r[title].objects.push(name);
        });
        return r;
    }, {}));

console.log(subs);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Feb 26, 2020 at 13:29

Nina Scholz

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Comments

Miaplacidus · Accepted Answer · 2020-02-26 13:47:27Z

1

Repl Example

let mySubs = myObjects.reduce((_mySubs = [], myObjectValue) => {
  myObjectValue.subs.forEach((sub) => {
    let mySub = _mySubs.find((myObject) => myObject.title === sub.title)
    if(!mySub) {
      mySub = {
        title: sub.title,
        objects: [],
      }
      _mySubs.push(mySub)
    }
    mySub.objects.push(myObjectValue.name)
  })
  return _mySubs
}, [])

answered Feb 26, 2020 at 13:47

Miaplacidus

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Comments

Scott Sauyet · Accepted Answer · 2020-02-26 14:03:15Z

A slightly different approach from the other answers:

const extractSubs = myObjects => 
  Object .values (myObjects .reduce (
    (a, {name, subs}) => subs .reduce (
      (a, {title}) => ({... a, [title]: {title, objects: [...((a [title] && a[title].objects) || []), name]}}),
      a
    ),
    {}
  ))

const myObjects = [{id: '1', name: 'name1', subs: [{id: '1', title: 'subName1'}, {id: '2', title: 'subName2'}]}, {id: '2', name: 'name2', subs: [{id: '2', title: 'subName2'}, {id: '3', title: 'subName3'}]}]

console .log (extractSubs (myObjects))

.as-console-wrapper {max-height: 100% !important; top: 0;}

As always, I prefer to encapsulate such transformations into functions. And I prefer not to mutate data any more than necessary. This is likely less efficient than other techniques, but I would go for this simple approach unless testing determined that it was a bottleneck in my application.

muZk · Accepted Answer · 2020-02-26 18:47:40Z

A possible solution with lodash:

_.chain(myObjects)
  .map(myObject =>
    myObject.subs.map(sub => ({ object: myObject.name, title: sub.title })),
  )
  .flatten()
  .groupBy('title')
  .map((data, title) => ({ title, objects: _.map(data, 'object') }))
  .value()

Full example:

const myObjects = [{
    id: '1',
    name: 'name1',
    subs: [
        {
            id: '1',
            title: 'subName1'
        },
        {
            id: '2',
            title: 'subName2'
        }
    ]
},
{
    id: '2',
    name: 'name2',
    subs: [
        {
            id: '2',
            title: 'subName2'
        },
        {
            id: '3',
            title: 'subName3'
        }
    ]
}]

const result = _.chain(myObjects)
  .map(myObject =>
    myObject.subs.map(sub => ({ object: myObject.name, title: sub.title })),
  )
  .flatten()
  .groupBy('title')
  .map((data, title) => ({ title, objects: _.map(data, 'object') }))
  .value()
  
console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

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